I need to replace the ignition switch wiring on my Mitsubishi D1650FD (the wires burned up due to an apparent dead short). The wiring diagram I was able to find indicates that the glow plugs are powered in the CCW momentary switch position and when the switch is in "run" position. Is this correct? My tractor, of course, runs when the switch is in "run" or "off" after it is started. Why would I want the glow plugs on once the tractor is started? Also, If I were to pull the head, at is it absolutely necessary to replace the cylinder head gasket? They are rather expensive by my standards. I'm pretty new to diesel engines... Thanks.